This Invention relates to hydraulically powered motors for accessory drives and more particularly to a new and improved multi-vane hydraulic motor with a hydraulically balanced rotor for improved high pressure performance and advanced pressurization of the undervane for quick and effective motor priming and efficient motor operation.
Prior to the present invention a variety of hydraulic motors have been devised to provide improved drives in various systems such as the hydraulic accessory drive system in automotive vehicles. Many of such motors are multi-vane units that utilize a rotor with an arrangement of outwardly-extending and reciprocally-movable vanes that have cooperating springs for exerting a yieldable outward spring force on the vanes. This force fully maintains the vanes in good sealing and sliding contact with a surrounding outer cam for efficient motor operation. Some problems have been experienced with some motors with vane biasing springs in high cyclic and high speed operation. For example, the vane springs for engine cooling fan drive motors may fatigue and have shortened service life because of high speed and cycle actions during vehicle operation. Such spring fatigue may cause poor motor performance or break down.
FIG. 7 of the drawings of this application illustrates one prior art motor with spring biased radial vanes. Other examples are illustrated and described in U.S. Pat. No. 5,470,215 issued Nov. 28, 1995 to Stephen Stone for Wear Resistant Vane-Type Fluid Power Converter and U.S. Pat. No. 5,702,243 issued Dec. 30, 1997 to C. Richard Gulach for Hydraulic Motor with Pressure Compensated End Plates.
While such prior art hydraulic motors have generally met their objectives in providing improved operating characteristics, more economical and efficient motors are needed to meet requirements for a wider range of applications and to meet higher standards from an efficiency, service life and cost standpoints. Moreover, manufacture and assembly of prior art motors with their special vane and spring constructions are tedious, difficult and costly. New and improved motors are needed to alleviate such problems.
In contrast to the prior art multi vane hydraulic motors exemplified above, the present invention provides a new and improved hydraulic motor of straight-forward construction with effective and efficient routing of hydraulic motor drive pressures for quickly stroking the vanes into operative sliding-sealing engagement with a surrounding cam surface for quick motor priming. With the hydraulic biasing of the vanes of this invention, wear is materially reduced. This invention furthermore advantageously utilizes a minimal number of components particularly as compared to the prior art constructions with spring biased vanes.
This invention accordingly provides for the effective elimination of vane springs with the optimized employment of hydraulic forces instead of mechanical spring forces for yieldably stroking or urging the vanes into operative sealing engagement with an outer cam ring. Moreover with the quick stroking or xe2x80x9cpop outxe2x80x9d of vanes with high pressure hydraulics, initially fed at elevated points on the pressure grade curve to the undervane, the specialized prior art vanes and springs and their mechanical attachment are no longer required for quick and optimized motor priming. With the effective elimination of such springs and their attachment constructions, potential sources of motor wear and breakdown are eliminated.
In this invention high pressure hydraulic fluid from a hydraulic pump feeds into the inlet port of the motor and then into the high pressure side chambers or balancing pockets formed on opposing sides of the rotor of the motor. These side chambers are interconnected by the undervane passages so that a hydraulic pressure on opposing sides of the rotor is the same and rotor balancing is achieved. With such balanced rotor, motor breakdowns such as from rotor seizure experienced by prior unbalance rotors is minimized. The undervane passages in the rotor are formed at the inner ends of outwardly extending slots in the rotor. The vanes are mounted for reciprocal movement in these slots and the outer tips thereof operatively engage the cam surface of a surrounding cam ring mounted in the motor housing. The porting of high pressure flow into the rotor balancing chambers and interconnecting undervane passages of the rotor further forces the vanes outwardly and the tips of the vanes against the interior contour of the outer cam ring to effect an optimized sliding fluid seal.
In one preferred embodiment of this invention, an open ended housing is provided in which a specialized disk-like pressure plate is fixed at a predetermined distance from an internal end wall as determined by radial inner and outer o-ring seals to define a high pressure drive chamber therebetween located at one side of the rotor. The rotor is operatively mounted within the housing on an output shaft which extends axially therefrom for driving an accessory such as an engine cooling fan. The housing is closed by an end plate fixed thereto at the other side of the rotor which is formed with the inlet and outlet passages therein for the connection of hydraulic input and return lines thereto.
As the rotor is rotatably driven by the feed of pressurized hydraulic fluid from the high pressure drive chamber through one or more routing passages in the pressure plate into the vane chambers, the vanes reciprocate in their slots to establish an endless series of sealed rotor-drive chambers between adjacent vanes. These chambers serially receive pressure fluid from the system pump via the internal passages in the motor including the rotor balancing pressure chambers and the connecting undervane passages that feed into the high pressure drive chamber through inner passages in the pressure plate. The vane chambers subsequently discharge such fluid into an exhaust passage system in the end or cover plate and then to the return line operatively connected thereto.
The flow through the vane chambers with minimized leakage past the vane tip and cam seal effects rotation of the rotor and attached output shaft for accessory drive. Importantly in this invention the undervane passages receive pump pressure at high and optimum points on the pressure gradient for exerting an equal and outward force on each of the vanes optimizing and equalizing vane fluid sealing and wear. With improved vane-cam ring wear and sealing, pump operation is optimized.